very nice! I think rice paper should also do the job. theres different types, but theres very fine rice paper. it doesn tear easily because the fibers so strong.
Just use masking tape on both sides. The Paper Cone is stiff, and the tape is thick and flexable. Make sure the sticky side is rubbed tight to the paper surface, to prevent peel. Had to increase video speed, to get thru your demonstration. Everybody has some complex method to fix a rip tear. Cloth Tape will also work. I used flex black silicone, on another. I think tape is best.
To much paper,, What I would have done after the patch on the back is dilute some more glue and lightly coat the back side of the cone just enough for the glue to soak into the cone paper fibers. then run a thin bead of super glue along all the cracks on the front of the cone about 1/4" past the ends of the cracks to stop them from running. Less is always best, as now one side of the cone is way thicker than the other.
But interestingly enough, I have two identical speakers, and the one I repaired sounds better. Thicker, richer, smoother. I think it's for the exact reason that the speaker is asymmetrical. Either way, the repaired speaker that I was going to sell, is now a keeper!!